Automatic and semiautomatic telephone plant



Oct. 3, 1933. D. c. CROWE 1,928,349

AUTOMATIC AND SEMIAUTOMATIC TELEPHONE PLANT Filed July 7, 1930 2 Sheets-Sheet l Oct. 3, 1933- c c ow AUTOMATIC AND SEMIAUTOMATIC TELEPHONE PLANT Filed July 7, 1930 2 SheetsSheet 2 lA/MEM Tue 5 Y 1 Fri ya Patented Oct. 3, 1933 P T T IC 7 1,923,349 AUTOMATIC AND sEMmUToMATIo TELE- PHONE PLANT I Douglas Cormack Crowe, Stoekholnn'Sweden, as-

signor to Telefonaktiebolaget L. M. Ericsson, Stockholm, Sweden, a company of Sweden Application Jury 7,1930, Serial N0.l466',2 66, and in Sweden July 9, 1929 V 4 Claims. (Cl. 17927) The present invention relates to switching are rangements in automatic and semi-automatic telephone plants. More particularly the invention relates tosuch plants in which both ordifyia nary talking connections and privileged or pr ferred calls, by way of example inter-omce con nections, may be established over the same selectors. The invention is substantially characterized in that the test circuits of the selector, at .10. the setting of the selector in a definite position, are automaticallyshifted in such' a manner that the connection may be established with a wanted line even when the latter is engaged by a conver sation which is not an inter-o'fiice one. The set 151 ting of the selector in said position is preferably brought aboutby an additional impulse series which has (no correspondence in the subscribefs number the system being then arranged in'such a manner that theselector, after it has been set '201 by said impulse series in the position in question and caused shifting of the test circuit, is automatically restored to the starting position so that it thereupon may be set in ordinary manner by a new impulse series. The shifting. position in question may be any one of the setting positions of the selector. Preferably the selector is provided with an additional setting position so that the'norrnal capacity of the selector is not reduced. In selectors having by way of example,

ten setting positions in one or more directions an eleventh setting position is thus preferably pro"- vided, the setting of the selector in this position then being brought about by an impulse series comprising eleven impulses. .Atthe same time a The additional impulse series intended to bringabout the shifting of the testing circuit must, of 7 .course, be sent in each point of the talking connection where an inter-ofiice call should be preferred. If the operator hasa finger disc, she 50. sends consequently by means of said disc an additional impulse series at each occasion when preference is wanted for'an inter-office call. If the operator has a register and a key set the sending of theadditional impulse series may take place automatically by a special-marking by means of a key in connection with the registra-' tion of the subscribers number.

If the additional impulse series in question. comprises a number of impulses which could be reproduced by the subscriber, special measures must be taken to prevent that a subscriber having knowledge of the system may be able to establish an undue connection. For this purpose special measures are taken, according to the invention, so that upon setting theselector in the shifting position in question a current impulse ora signal is sent to switching members disposed at the calling end of the talking connection which members may interrupt the connection or prevent its completion. The system is arranged (0 in such'a manner that said impulse or signal is inoperative at inter-ofiice communications established from an inter-ofiice operatorvbut, on the. other hand, will be operative at all communications established from a subscriber or another 75. undue calling place.

Bythe above described arrangements .it is rendered possible, as mentioned above, to -establish an inter-'oifice connection with asubscriber even if he for the time being is engaged by acommunication not being an inter-oilice one. The inter-orifice operator may then atwill break the already established connection which may take place either automatically immediately upon the connection tothe sub'scribersline or through a special switchingioperation after effected connec- When the called subscriberafter completed call rehooks the micro-telephone a signal is generated which is repeated back and causes a clearing signal at the operators position; Said signal is removed if the subscriber again lifts off the micro-telephone. The subscriber may in this manner call the operators attention without interrupting the communication. After the subscriber has completed the conversation by rehooking the micro-telephone the operator may again call the subscriber when required.

The invention will be more closely described with reference to the accompanying drawings showing a part of a talking connection established over two telephone exchanges. Figure 1 shows the relays in circuits appertaining to the outgoing junction line-whereas Figure 2 shows a final selector together with the appertaining relays and circuits. r

A calling subscriber may in a manner known per se obtain-connection from his apparatus A to a junction line FL extending to another telephone exchange over his subscribers line AL and one or more selectors. In the shown example only the contact arms of a call finder AS and a group selector GV are shown. The junction line FL and the appertaining relay set are connected to the contact field of the group selector through a junction AFL consisting of four wires a, b, c, d, and also to the inter-office operators desk EP through a similar quad-wire junction line EFL} The junction line FL is in usual manner provided with a relay RA included in the microphone circuit of the calling subscriber which relay at its contact 1 controls thecircuit extending over the junction line which circuit in usual manner-is separated from the microphone feeding circuit of'the subscriber by condensers Ka,

' issent from an inter-office operator, no eflicient blocking takes place because the short-circuit is of a very short duration. If, on the other hand, the callis sent from a subscriber unduly trying to establish the desired communication a durable blocking is obtained'as the relay RS is then locked in -energized position. The holding circuit of the relay RB is for this purpose controlled by a relay JBR actuated only upon calls from an operators position and which at its contact 4 interrupts said holding circuit but upon calls from a subscriber remains inoperative and consequently causes blocking.

.The'line selector LC, Figure 2, consists in the shown example of arelay selector of the'kind describedin the U. S. Patents Nos. 1,645,89 '7 and 1,659,627. 1 The selector comprises a socalled multiple relayprovided with ten relay armatures and a corresponding number of con tact spring groups KS'actuated by said armatures and a magneticcircuit common to all armatures and provided'with amagnet winding CM which is throughout wound in thesame direction on one and the same magnetic core and at both ends connected to the negati've'pole of the central battery. At the points designated by the numerals 1', 2, 3 etc. said winding is provided with tappings over which the magnet winding may be connected to the positive pole ofsaid-battery. The selector is adaptedto beset by means of impulses overa circuit controlled byithe different armatures in :such. a manner that the armatures are sequentially attracted and released respectively by the infiuenceof the successive impulses. For this purpose the selector is provided with a numceases.

ber of shifting contacts 0K, viz. a group of shifting contacts for each armature which contacts are adapted to control the impulse circuit in such a manner that said circuit is successively extended to the different branching points. The first impulse, incoming at the contact group 0K1, is branched off at the branching point 1 so that the current passes in opposite directions through the parts of the winding CM disposed on opposite sides of said point, a pronounced magnetic pole then being established at the point 1 and the corresponding armature actuated. The system is then so arranged that the contact spring group 0K1 is not actuated before the current impulse When the impulse has ceased, a shifting takes place so that the impulse circuit is extended to the impulse contact 0K2 and over said contact to the other branching point 2. The other current impulse will consequently bring about a pronounced magnetic pole at the point 2 whereby the other armature is actuated. When the second current impulse ceases the circuit is extended in similar manner to the third shifting contact OK: and over said contact to the third branching point 3, the third current impulse will thus actuate the third armature, etc.

In the example shown on the drawings the tenth setting position of the final selector LC is intended to be used for shifting the test circuits of the final selector by an additional impulse series to mark an inter-office call in above described mannerJThe final selector is for this purpose in the tenth position provided with a contact 5 over which a relay JA may be actuated to bring about said shifting. To mark inter-ofiice calls, relays JB, JD, JE and JG are also provided. The circuit extending overthe junction line includes in ordinary manner a relay Aa which together with the relay I serves to transmit the impulses to the final selector. The supply of current to the called subscriber takes place in known manner through the windings of a relay Ac. The disposition of the circuit and the operation of the switching member included therein is, for the rest, readily understood by the following description of the switching operation.

Initially it may be assumed that an inter-office communication has to be established from the operato'rsposition EP. Then a circuit 6 is first closed through the relay RA. At the same time a circuit 'lis closed through the relay J BR which is energized and at its contact 8 closes a circuit of a relay SBR which is also energized. The relay JBR connects the positive pole of the battery over the relay contact 8 to the third wire 0 of the junction line AFL over a resistance 11 whereby the junction line PL is marked as engaged in all the selectors R in which the junction line AFL is multiplied. When the relay RA was energized a circuit 10was closed through a slow-acting relay Rv'which now closes a circuit 11 over the wire d of the junction line EFL whereby said line is marked as engaged. The relay RA has further, at its contact *1, closed the circuit 12 extending over the junction line FL and containing the relays RD zand Aa. The former relay connects the relay RQ over a circuit 13; The relay Aa has meanwhile closed a circuit 17 through a. slowacting relay K which in turn has closed the circuit 18 through a slow-acting relay D.

The inter-ofiice operator thereupon sends a series of ten'impulses intended to bring about said'shifting of the circuits of the final selector. The first current interruption in-the line circuit causes de-energization of the relay RA'which in turn interrupts the circuit 12 over the junction line. The relay RA at the same time closes a circuit 14 through a relay RV and a holding winding of the relay RD, whereby the latter relay is prevented from bein'g'immediately de-energized. The relay RV connects itself into a holding circuit 15'and short-circuits at its contact 2 the operati've winding of the relay RD which is now deenergized, after the holding circuit 14 has also been interrupted at the contact 16 of the relay- RV. During the impulse sending the relayRQ is de-energized 'over the circuit 9. On account of the interruption in the junctionline circuitnow also the relay Aa is de-energized. When the latter relay is de-energized, a circuit 19 is closed through the relay I. The relay K holds its armature attracted during the impulse sending. The relay I closes in turn a circuit 20 through a relay B which is energized. When the relay Aa is again energized the relay I is de-energized a circuit 21 being then formed containing windings of the relay B and C. The relay B is thereby locked in attracted position, whereas the relay C is energized and locks itself over a circuit 22.

When the relay I is de-energized a circuit 23 is formed through the magnetizing winding CM of the final selector. As a consequence, the first armature of the selector is attracted. The secprepared to receive the second impulse. the second current interruption ceases and the 0nd current interruption in the line circuit causes now de-energization of'the relay Aa, the relay I then again being energized and the relay D being held over the circuit 24. When I is energized the relay B is de-energized, which thereline circuit is again closed the relay Aa is again energized. Then the relay I is de-energized which now closes a circuit 26 through the second branching point of the magnet winding CM of the final selector. The following current interruptions in the line circuits willnow cause an alternate making and breaking of the impulse circuit 26 of the final selector so that the relay armature of the final selector is successively re- When the tenth armature of the final selector leased and actuated.

is actuated a circuit 27 is formed over the contact 5 in the tenth position. The latter circuit in- Mf cludes the operative winding of the relay JA which is now energized and closes a circuit 28 through the operative winding of the relay JE. When thus all impulses have been sent the relay RQ, Figure 1, is de-energized, the circuit 14 through the relay RV being then interrupted. The latter relay is then, as a consequence, de-

energized and removes the short-circuit of the operative winding of the relay RD which is then de-energized. Then the relay RQ receives again current over the circuit 13. When the relay I, Figure 2, is de-energized also the relay B is deenergized after a short moment. After another moment also the relay C is de-energized the circuit 22 being interrupted at the contact 29 of the relay D. The relay B is now instead energized over the circuit 18. When the relay C is de-energized, the circuit 27 of the relay JA is'interrupted which relay is thus de-energized. The relay C also interrupts the'circuit 26 of the final selector at its contact 30 the tenth armature o! the selector being then released. At the same time the relay JE receivesholding current over the circuit 31. I

The setting of the final selector in the tenth position resulted, as mentioned, in that the relay JA was energized and after a short moment again de-energized. Hereby a blocking impulse is sent back over the talking connection in the following manner: When the relay JA is energized a short-circuit is established at the contact 32 of said relay over the two branches of the junction line whereby the relay RD is de-energized. Then a circuit 33 is closed through a relay RY which is now energized and closes a circuit 34 through two relays Ra and Rb. The latter relays are energized and connect themselves into a holding circuit 35. Then a circuit 36 is closedthrough the relay RS which now is energized and shortcircuits the impulse contact 1 of the relay RA. Said blocking impulse is repeated by the relay RB by short-circuiting both talking line branches of the junction line EFL over the contact 37 of the relay B. The blocking impulse causes, however, in this case no blocking because the relay B is again de-energized when the relay JA, Figure 2, is de-energized. When the relay RB is deenergized the circuit of the relay RQ was interrupted which after a moment is de-energized the circuit 36 being then interrupted and the relay B de-energized. When the relay JA, Figure 2, is de-energized, the short-circuit of the, junction line is removed and the relays RD and RQ are again energized. The relay RD then interrupts the holding circuit of the relay Ra and Rb which are thus de-energized.

The final selector may now be set by means of a new impulse series to bring about connection to the wanted subscribers line' BL. The setting of the final selector takes place in above described manner. It is assumed that the selector is then set in the seventh position. After all the impulses have been sent the relay D is de-energized a circuit 38 being then formed through a relay P which is de-energized and locks itself over a circuit 39. When the relay D is de-energized also a test circuit 40 is closed over the third wire 0 and the calling subscribers cut-off relay BR which circuit also includes a winding of the test relay JG. 7

Initially, it may be assumed that the calling subscriber is not engaged by any conversation. The relay JG will then be energized, said relay then connecting itself into a holding circuit 41. In the latter circuit the relay JD is parallel connected with the holding winding of the relay JG for which reason also the relay JD is de-energized. The latter relay interrupts at its contact 42 a short circuit 43 over the operative winding of the relay G the relay G then being energized and locking itself over a circuit 44 including the cut-off relay BR. The relay G closes at the same time a circuit 45 through a buzzer current source RT to mark the calling signal which circuit includes a winding of the'relay Ac through which a signal current is induced in the line circuit. When the relay C after a moment drops its armature the circuit 31 is closed through the relay JE. When the relay JE in turn is de-energized after a moment a holding circuit 46 is closed through the holding winding of the relay G. At

the same time the c-wire is connected to earth over a current path 47 whereby the subscriber ismarked as engaged by an inter-ofiice call.

When the'relay JE is de-energized a calling circuit 48 is closed over the called subscriber's line which circuit includes a calling current source RGI sending a calling signal particularlyadapted for inter-ofi'lce calls. Said circuitv includes, also the two windings of the relay R which, however, isnotactuated by the calling current so long as the called subscriber hasnot answered. When the subscriber answers by lifting the micro-telephone the calling current is amplified through the relay R so that said relay is energized, the circuit 39of-the relay P being then interrupted. When the relay P as a result is de-energized the calling circuit. 48 and the buzzer circuit are interrupted. The relay R locks itself over the circuit 49. When the subscriber answers his microphone circuit 50 is closed through the relay Ac which at its contact 51 connects the one winding. ofthe relay 'Aa to the a-branch of the junction line. By this the talking connection is completed.

When Ac is energized a circuit 52 is closed through the relay JF, which is energized and interrupts-the circuit of the relay R at its contact 53 whereby the relay R is de-energized. During the time of the relay R being energized the bbranch of the junction line is directly connected to earth over the-circuit 54. Thereby a signal is sent back to the calling end of the talking connection in the following manner. The relay RD is de-energized because thetwo branches of the junction'linenow are connected-to earth. Then the circuit 33 is again closed through the relay RY which is energized and connects the two relays Ra and Rb to the two branches of the junction line. In this case only the relay Ra is, however, actuated, which relay now closes a circuit 55 through the relay RM. The latter relay is'energized and connects the b-wire of the junction line EFL to earth at its contact 56 whereby the signal is thus repeated'through the operators position, where it may be used to actuate a signalling lamp whereby the operator is inforniedthat the called subscriberhas answered. At calls from a subscriber said signal may instead be used to actuate the call meter to registerithe call.

When the called subscribed after completed conversation rehooks the micro-telephone, the relay Ac is de-energized. The latter relay then interrupts at its contact 51 the connection between the positive'pole of the battery and the a-branch of the junction line whereby a signal is sent back to the calling end of the connection in the following manner. The relay D is de-energized and connects the relay RY into circuit which connects the two relays Ra and Rb to the junction line. In this case only the relay Rb is actuated and closes a circuit 57 through a relay RC which at its contact 58 brings about a corresponding interruption in the a-branch of the junction line EFL. The signal transmitted in this manner is utilized to actuate a clearing signal at the operator which is thus informed that the called subscriber has completed the conversation. When the relay Ad is de-energized a circuit 59 is closed through the relay P. I

' The operator may now again call up the subscriber, for instance by sending an impulse over the line circuit by means of the finger disc. When the relay Aa as a consequence is de-energized the relay JF is de-energized, because the holding circuit of said relay is interrupted at the contact 60. Consequently the inter-office calling circuit is now again closed over a contact of the relay JF and the subscriber is again called up.

When the subscriber answers by lifting the nicro-telephone the calling signal is disconnected as before. I

If the subscriber is assumed to be engaged by a conversation which is not an interoflice one the following switching operation will take place after all the current impulses have been sent. When the relayD'is de-energized the relay P is de-energized as before. The testing relay JG receives also now sufiicient current to be energized because it is now parallel connected with the resistance included in the testing circuit of that line with which thesubscribers line now communicates. The relay JG is consequently energized, also the relay JD being in above described manner operative. 1 When the latter relay now interrupts the short-circuit over the relay G said relay receives, however, not suflicient current to be able to attract its armature, because the test relay in the already existing connection is included as a shunt across the test circuit in question. -When the relay G after a moment is deenergized a circuit 61 is formed through the relays JA and 58 which are energized. The relay JB locks itself overits contact 62 and the contact 60. of the relay Ad. The magnetizing circuit of the final selector receives now holding current over a contact-of the relays K and JG and over the resistance F. When the relay J B is energized also the relay R is connected into circuit over the contact 63 of the relay JB the relay R then locking itself over its contact 64 and the contact 53 of the relay JF. When R is energized the circuit through the relay P is interrupted at the contact .65. When the relay, as a consequence, isdeenergized the circuit through the relay JA is interrupted at the contact 66 of? for which reason also the relay JA after a moment is de-energized. During the time of the relay JR being de-cnergized the junction line is shortcircuited at the contact 32. Hereby a signal is received as before which is repeated back and whereby the subscriber is informed that the connection is completed. The subscriber is now over the condensers Ca andCb and the contacts 67, 68 of the relay JB connected to the already existing connection so that the operator may com inunicate with the wanted subscriber.

When the connection has to be interrupted this may be effected by that the operator, by way of example, by'means of her finger disc brings about one or more current interruptions in the line circuit. When the relay Aa, as a consequence, is de-energizcd the circuit of the relay JB is inter.- rupted at the contact of the relay Aa the relay JB being then tie-energized. The relay JE now receives holdingcurrent over its contact 69 the contact '70 of the relayJB and the contact '71 of the relay A'a. When the relay Ad is again energized the circuit through the relay JE is interrupted at the contact 7 1 for which reason the latter relay after a moment is ole-energized. Then a circuit 72 of the test relayG is closed. When the relay G, as a consequence, is energized the c wire is directly connected to earth over a circuit '73 the existing connection being then interrupted by the test relay of the called subscriber being short-circuited. When the relay G is energized also the relay Ac is connected into circuit over the line circuit the relay JF obtaining current over the circuit 52. Then the circuit through the relay R is interrupted at the contact 53 whereby the relay R after a short moment is de-energized. When the relay (3 is energized also the b-wire of the junction line is connected to earth over'a contact 75 of the relay G and the contact 76 of the relay R whereby an answering signal is received which ceases when R is de-energized and which is repeated 'to the operator. The inter-office communication is thereby completed.

If the calledsubscriber already is engaged by an inter-oflice conversation the c-wire is directly connected to earth. When the relay B after com pleted impulse sending is ole-energized the relay JE is thus short-circuited. The relay P is de-energizecl as before and, a buzzer circuit for busymarking is closed through the buzzer winding of the relay Ac over the contact 77 of the relay P and the contact '78 of the relay G through a buzzed current source BT. When the relay C after a moment is de-energized also the relay JE is de-energized. The connection is then cleared through interruption of the line circuit.

It may now be assumed that the subscriber A unduly tries to establish a communication with another subscriber by sending an additional series of impulses. The switching then proceeds in substantially the same manner as above described as regards calls from an inter-ofilce operators position with the difference that in this case only the relay SBR is actuated whereas the relay JBR remains de-energized. After sending the first impulse series a blocking signal is sent back, as in the former case, over the junction line by that the relay JA for a moment short-circuits both branches of the junction line. Then the'relays Ra, Rb are actuated in above described manner which relays in turn close the circuit 36 of the relay RB. When the latter relay is energized it connects itself into a holding circuit 79 which remains closed so long as the calling subscriber holds his micro-telephone lifted. The relay Rb short-circuits at its contact 3 the impulse contact 1 of the relay Ra whereby all further impulsing from the subscriber is prevented.

The invention may, of course, also be applied in systems having mechanical selectors, by way of example such group and final selectors which may be set in one direction to select the wanted line group and in another direction to select the wanted line. In selectors of the latter kind the arrangement is preferably disposed in such a manner that'the shifting of the test circuit is brought about by a preparatory setting of the selector to a certain position in the motion direction in which the selector is set at first to select the desired line group whereupon the selector is restored to be able to be set anew to select the wanted line group. If the first setting position is used as shifting position the selector needs not be restored but it may be set anew from said position as a starting position. i

I claim:--

1.'In a telephone system in which ordinary talking connections and so-called privileged or preferred connections, by way of example interofiice connections, may be established over the same selectors, a telephone line, a selector connected thereto, switching elements appertaining to the selector, means to actuate said switching elements to shift the test circuits of the selector automatically so as to allow establishing of a communication with a line also when the latter is engaged by a conversation which is not an interofiice one, a bank contact associated with the said switching elements, means to set the selector by a preparatory movement under control of numerical impulses on the said contact so' as to obtain the said shifting of the test circuits of the selector before the selector is taken into use for its selecting purpose.

2. A telephone system according to claim 1, in which the selector is provided with a special contact position in which it may be set by means of a series of current impulses comprising more than ten impulses.

3. In a telephone system in which ordinary talking connections and so-called privileged or preferred connections, by way of example interoflice connections, may be established over the same selectors, a telephone line, a selector con-' nected thereto, switching elements appertaining to the selector, means to actuate said switching elements to shift the test circuits of the selector automatically so as to allow establishing of a communication with a line also when the latter is engaged by a conversation which is not an inter-office one, a bank contact associated with the said switching elements, means to set the selector by a preparatory.movement under control of numerical impulses on the said contact so as to obtain the said shifting of the test circuits of the selector before the selector is taken into use for its selecting purpose and means to automatically restore the selector to starting position.

4. In a telephone system in which ordinary talking connections and so' called privileged or preferred connections, by way of example interoffice connections, maybe established over the same selectors, a telephone line, a selector connected thereto, switching elements appertaining to the selector, means to actuate said switching means to shift the test circuits of the selector automatically upon setting the selector under control of numerical impulses'in a definite position, so as to allow establishing of a communication with a line also when the latter is engaged by a conversation which is not an inter-office one, I

means to restore the selector to starting position, and means to shift the test circuit of the selector by a preparatory setting of the selector to a certain position during the group selecting movement of the selector.

DOUGLAS CORMACK CROWE. 

